Antimicrobial composite

ABSTRACT

An antimicrobial composite which comprises a first, liquid-permeable layer and a second layer arranged on the first layer. An antimicrobial metal in elemental form is present between the first and second layers and substantially no antimicrobial metal in elemental form is present on exterior surfaces of the composite. This abstract is neither intended to define the invention disclosed in this specification nor intended to limit the scope of the invention in any way.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority under 35 U.S.C. § 119 ofGerman Patent Application No. 103 28 261.0, filed on Jun. 23, 2003, thedisclosure of which is expressly incorporated by reference herein in itsentirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to antimicrobial composites whichmay be used, in particular, as wound coverings, dressings, cloths, andthe like. By coating one side of a liquid-permeable material with anantimicrobial metal such as silver and laminating the resultant materialto a material such as a liquid-absorbing nonwoven material with themetal coating facing the liquid-absorbing material, the abrasion ofmetal particles may be prevented while at the same time, theantimicrobial and disinfectant effect of the metal coating is retained.

[0004] 2. Discussion of Background Information

[0005] Treating and healing bacterially contaminated skin and wounds, orinfected skin and wounds is a major challenge to medicine and thenatural sciences. Poorly healing and chronic wounds frequently becomepopulated by a wide variety of microorganisms that considerably delayhealing and sometimes even prevent healing altogether. Frequently, inthe case of acute wounds that are caused by trauma, surgicalintervention or even just simple injury, the penetration and infectionby pathogenic microorganisms can, however, not completely be prevented.

[0006] Various possibilities are described for removing microorganismsfrom the contaminated or infected tissue of a wound and/or for killingthe microorganisms. In addition to the oral administration ofantibiotics, the removal of pathogenic microorganisms from a wound maybe achieved, in accordance with the prior art, by the topicalapplication of a disinfectant or an antibiotic. However, antiseptics andantibiotics are cytotoxic; in addition, many pathogenic strains havedeveloped resistances to antibiotics.

[0007] An example of the known antimicrobial and/or prophylactictreatment of contaminated or infected wounds is the use of oxidants suchas tincture of iodine, or of antiseptics such as ointments which containsilver sulfadiazine.

[0008] For a very long time, silver has been the agent of choice fortreating infections, due to its broad bactericidal and fungicidaleffect. In addition to its broad range of activity, silver is effectivein minute, i.e., trace amounts (oligodynamic effect). Since the amountsof silver are so small, the tolerance is excellent. For example, silveraerosols, silver-containing solutions, ointments or tablets, etc. arewidely used as antiseptics.

[0009] Silver-containing products are also used in the form ofcorresponding antimicrobially treated or impregnated wound dressings andwound care materials. The use of silver-containing zeolites, glasses andzirconyl phosphates, and also of silver in elemental or nanocrystallineform, is known as well.

[0010] Basically, there are two forms used for the administration ofsilver (ions), i.e., forms in which the silver ions are present in theproduct per se, and forms in which the ionic form of silver is generatedby the oxidation of elemental silver. The first case essentiallyinvolves a dissolution or ion-exchange process. This makes the silverions rapidly available, but the amount of silver ions in the preparationdrops quickly as well. To provide a sufficient amount of silver tocounteract this disadvantage is not without problems. For example, thecytotoxicity of silver ions limits the maximum acceptable amount thereofthat can be used in a product.

[0011] Another disadvantage is that silver is deactivated by proteins,other complex-formers, or in the presence of ions that formscarcely-soluble silver salts. These conditions doubtlessly exist inwound fluids. In contrast, the release of silver from “elemental” silver(silver metal) is slower and occurs over a longer period, but takesplace continuously. Accordingly, a sufficient amount of silver ions thatis harmless to the user can always be released from the reservoir ofelemental silver, the amount of silver ions depending on whether more orless of these ions can be released by equilibrium processes. The releaseof silver is, therefore, “as needed,” and the release of an effectivequantity of silver is ensured.

[0012] An overview of known antimicrobial, silver-containing wound carematerials is given in DE-A1-19958458.

[0013] A commercially available wound care product with antimicrobialproperties is known under the name of Arglaes®. Its mode of action isbased on “slow-release polymer” technology that causes a slow butconstant release of silver ions in the moist milieu of the wound(Biomed. Mat., Nov. 1995; Health Industry Today, 1 Nov. 1997, Vol. 58,No. 11).

[0014] DE-A1-19958458 discloses wound coverings comprising a syntheticpolymer material which contains metal ion-containing zeolites.

[0015] Silver-containing glasses that have an antimicrobial effect areknown from EP-A1-1116698 and EP-A1-1116700. These glasses are embeddedin thermoplastic polymers that are used in a wide variety of forms forhousehold and hygienic applications such as wallpaper, cutting boards,etc.

[0016] U.S. Pat. Nos. 5,753,251 and 5,681,575 describe antimicrobialcoatings with so-called nanocrystalline silver that are formed on amedical product by depositing metals such as, e.g., silver from a gasphase. The antimicrobial effect is based on the release of ions, atoms,molecules or clusters from a disordered metal lattice when the silver isin contact with water or alcohol-based electrolytes. The correspondingproduct is known under the name Acticoat®. One of the disadvantages ofthis product is the visibly identifiable silver abrasion that causes ablack discoloration of the covered skin area.

[0017] U.S. Pat. No. 2,934,066 describes a wound covering coated withmetals, especially silver, which is reported to have a disinfectingeffect.

[0018] The entire disclosures of the documents cited above, as well asthose of all other documents mentioned in the present specification, areexpressly incorporated by reference herein as if each of these documentsin its entirety were part of the present specification.

[0019] Wound coverings comprising a non-woven material that is coveredwith a silver-coated polyethylene mesh are also known, e.g., Katomed®.

[0020] In all of the known disinfectant wound dressings which comprise acoating of elemental or nanocrystalline silver, the silver coating isintended to directly contact the wound. A disadvantage of thesedisinfecting materials is, therefore, that upon their contacting of theskin or wound they give rise to an abrasion and release of smallparticles of elemental silver. These particles form inclusions in theskin or wound, so-called granulomas, and can lead to complicationsduring wound healing. Furthermore, due to the generated blackdiscoloration, the aesthetic acceptance of corresponding products amongusers is very low.

[0021] It would be desirable to have available a material, e.g., a skinor wound dressing, which does not show the disadvantages of the knownmaterials, but nevertheless shows antimicrobial activity.

SUMMARY OF THE INVENTION

[0022] The present invention provides an antimicrobial compositecomprising a first, liquid-permeable layer and a second layer arrangedon the first layer. An antimicrobial metal in elemental form is presentbetween these layers. Moreover, substantially none of this antimicrobialmetal in elemental form is present on exterior surfaces of thecomposite.

[0023] In one aspect of the composite, the first layer may comprise aforamenous structure, and preferably comprises a hole structure and/or amesh structure. For example, the first layer may comprise a perforatedfilm and/or a mesh.

[0024] In another aspect of the composite, the first layer may comprisean organic polymer, preferably, a polyolefin such as, e.g., polyethyleneand/or polypropylene

[0025] In yet another aspect, the first layer may comprise apolyethylene mesh.

[0026] In a still further aspect, the first layer preferably comprisesopenings having a size of from about 250 μm to about 1400 μm, e.g., fromabout 400 μm to about 700 μm. In one embodiment, the openings may have asubstantially triangular shape and/or may provide an open area of fromabout 15% to about 60% of the surface area of the first layer.

[0027] In another aspect of the composite, the first layer may have athickness of from about 0.02 mm to about 0.8 mm, e.g., of from about0.05 mm to about 0.5 mm.

[0028] In a still further aspect, the second layer is a liquid-permeablelayer or a liquid-absorbing layer.

[0029] In another aspect, the second layer may comprise a perforatedfilm and/or a mesh.

[0030] In yet another aspect, the second layer may comprise an organicpolymer. The organic polymer may comprise a polyolefin. For example, thesecond layer may comprise a polyethylene mesh.

[0031] In a still further aspect of the composite of the presentinvention, the second layer preferably has a thickness of from about0.02 mm to about 2.5 mm.

[0032] In another aspect, the second layer may be a liquid-absorbinglayer. This layer may have a liquid-absorbing capacity of from about 300g/m² to about 2000 g/m², e.g., from about 400 g/m² to about 1000 g/m².For example, the liquid-absorbing layer may comprise a textile sheet,which textile sheet may in turn comprise a nonwoven, a fleece, a wovenfabric, a knit and/or a felt.

[0033] In a still further aspect, the second layer may comprise fibersand/or yarns.

[0034] In another aspect, the second layer may comprises viscose,polyolefin (e.g., polyethylene and/or polypropylene) and/or polyester.

[0035] In another aspect of the composite, the second layer preferablyhas a thickness of from about 0.3 mm to about 2.4 mm, e.g., from about0.5 mm to about 1.4 mm and/or an area weight of from about 80 g/m² toabout 200 g/m².

[0036] In a still further aspect, the second layer may comprise asuperabsorber, for example, a superabsorber comprising a polymer havingrecurring units derived from acrylic acid and derivatives thereof. Thesuperabsorber may be present in an amount of from about 0.01% to about40% by weight, based on the weight of the second layer.

[0037] In another aspect of the composite of the present invention, theantimicrobial metal preferably comprises at least one of Ag, Au, Pd, Pt,Cu, Ir, Zn, Sn, Sb, Bi and/or an alloy comprising one or more of thesemetals. Preferably, the antimicrobial metal comprises Ag and/or an alloythereof.

[0038] In yet another aspect of the present composite, the antimicrobialmetal may be provided as a coating on at least one of the surfaces ofthe first and second layers.

[0039] In another aspect of the composite, the antimicrobial metal maybe present as a layer which comprises the antimicrobial metal and isarranged between the first and second layers.

[0040] In a still further aspect, the composite preferably has asheet-like (web-like) structure.

[0041] In yet another aspect of the composite of the present invention,the antimicrobial metal (e.g., silver) preferably is present in anamount of from about 1 mg/m² to about 1 g/m² of composite, e.g., in anamount of from about 10 mg/m² to about 600 mg/m² of composite, morepreferably in an amount of from about 50 mg/m² to about 450 mg/m² ofcomposite, e.g., in an amount of from about 60 mg/m² to about 80 mg/m²of the composite.

[0042] In another aspect of the composite of the present invention, thefirst layer has a silver coating on the side (surface) thereof whichfaces the second layer and/or the second layer has a silver coating onthe side (surface) thereof which faces the first layer. In yet anotheraspect, an intermediate layer is arranged between the silver coating andthe first layer. The intermediate layer preferably comprises aluminum.

[0043] In yet another aspect of the composite, the composite preferablyhas an area weight of from about 50 g/m² to about 300 g/m², e.g., fromabout 80 g/m² to about 160 g/m², and/or a thickness of from about 0.4 mmto about 2.5 mm, e.g., from about 0.5 mm to about 1.4 mm, and/or apeeling strength of from about 0.05 N/cm to about 1.5 N/cm, e.g., fromabout 0.15 N/cm to about 0.8 N/cm, and/or a maximum tensile strength offrom about 10 N/cm to about 40 N/cm, and/or a 24-hour release of theantimicrobial metal (e.g., silver) of from about 0.05 mg/m² to about 3mg/m² of composite, e.g., of from about 0.1 mg/M² to about 2 mg/M² ofcomposite and/or a size of at least about 0.5 cm² and/or a size of nothigher than about 1 m².

[0044] The present invention also provides a wound covering article, askin care article and a diaper, all of which comprise the abovecomposite, including all of the various aspects thereof.

[0045] The wound covering article, for example, may further comprise abacking material arranged on the second layer of the composite. Thebacking material may carry an adhesive, e.g., a UV-curable acrylicadhesive or a rubber-based hot melt adhesive, on the side thereof whichfaces the second layer. Furthermore, the backing material preferablycomprises a polyester nonwoven and/or a polyethylene film.

[0046] The present invention also provides a method of covering a wound.The method comprises placing the above wound covering article, includingthe various aspects thereof, on the wound so that the first layer of thecomposite contacts the wound.

[0047] The present invention also provides a method of covering a wound.The method comprises providing a material which comprises aliquid-permeable layer and an antimicrobial metal in elemental formassociated with this layer (e.g., coated with the metal and/or havingthe metal incorporated therein and/or being in (direct) contact with themetal, etc.), and placing the material on the wound so that a surface ofthe liquid-permeable layer which is substantially free of theantimicrobial metal in elemental form contacts the wound.

[0048] In one aspect of the method, the liquid-permeable layerpreferably comprises a foramenous material, e.g., a hole and/or a meshstructure. For example, the liquid-permeable layer may comprise aperforated film and/or a mesh, e.g., a polyolefin mesh.

[0049] The present invention also provides a process of making anantimicrobial composite as set forth above. The process comprisesbonding together a first, liquid-permeable material and a secondmaterial which is liquid-permeable and/or liquid-absorbing. At least oneof the first and second materials is coated with an antimicrobial metalin elemental form on a side (surface) thereof which faces the othermaterial, whereas substantially no antimicrobial metal in elemental formis present on the exterior surface of the composite.

[0050] In one aspect, the process may comprise providing aliquid-permeable, sheet-like material, coating one side of the materialwith the antimicrobial metal and bonding a liquid-absorbing material tothat side of the liquid-permeable material which has the antimicrobialmetal thereon. The liquid-permeable material preferably comprises a holeand/or a mesh structure. In another aspect of the process, theliquid-permeable material may be coated with the metal by a techniquewhich comprises vapor deposition, e.g., by vacuum evaporation,sputtering, ion-beam assisted deposition, ion plating or magnetronsputtering.

[0051] In another aspect of the process of the present invention, theliquid-permeable material has an intermediate coating on that sidethereof which is to be coated with the antimicrobial metal. Theintermediate coating preferably comprises aluminum in metallic form.

[0052] In a still further aspect of the present process, theliquid-absorbing material and the liquid-permeable material are bondedto each other by lamination under heat and/or pressure, gluing, welding,and/or sewing.

[0053] As mentioned above, the first layer of the composite of thepresent invention is a liquid-permeable layer. The term“liquid-permeable” as used in the present specification and the appendedclaims is interchangeable with the term “fluid-permeable” and denotes amaterial which is capable of allowing liquid (fluid) such as water,wound secretions (wound exudate) etc., present on one side of thematerial to get to the opposite side of the material, irrespective ofthe way and/or mechanism through which this is accomplished.Accordingly, any material which is not completely impervious to liquid(fluid) is “liquid-permeable” for the purposes of the present invention.In this regard, it should be noted that a liquid-absorbing material maybecome liquid-permeable once the liquid absorbing capacity of thematerial is exceeded. Preferably, the liquid-permeable material has aforamenous structure, e.g., a hole or mesh structure. Non-limitingexamples of corresponding materials are a perforated film and a mesh.

[0054] The material of the first layer will usually comprise one or moresubstantially bioinert materials, e.g., a (natural, semisynthetic orsynthetic) organic polymer, preferably, a polyolefin such as, e.g.,polyethylene and/or polypropylene. However, materials different fromorganic polymers may be used as well, as long as they can be made tobe—or already are—liquid-permeable. If the composite of the presentinvention is to be used in wound-care applications, the material ispreferably substantially non-adhering to the wound.

[0055] Particularly in cases where the liquid-permeable materialcomprises a net, the openings thereof preferably have an (average) size(=length of the longest bisector) of at least about 250 μm, e.g., atleast about 400 μm, and not higher than to about 1400 μm, e.g., nothigher than about 1000 μm, or not higher than about 700 μm. The openingsmay be of any shape such as, e.g., circular, triangular, rectangular,etc., and different shapes and/or different sizes of openings may bepresent in the same material. Preferably, the open area created by theseopenings is at least about 15%, e.g., at least about 25%, and not morethan about 60%, e.g., not more than about 50%, of the surface area ofthe first layer. The same applies to other liquid-permeable structuressuch as, e.g., perforated films, although in this case the size of thehole openings may be by far larger than those usually encountered with anet structure (e.g., up to about 3 mm or even larger). Holes may becreated (e.g., in a film) by many different techiques, e.g., bymechanical perforation, punching, embossing, flame-perforation, etc.Moreover, holes may be present in the material from the beginning, e.g.,in the case of nonwovens (e.g., spun bonded nonwovens), and woven orknitted fabrics.

[0056] The first layer will usually have a thickness of at least about0.02 mm, e.g., at least about 0.05 mm, or at least about 0.1 mm. Usuallythe thickness of the first layer will be not higher than about 0.8 mm,e.g., not higher than about 0.5 mm, or not higher than about 0.3 mm. Itshould be noted that while it is currently preferred for the first layerto be composed of a single layer, the first layer of the composite ofthe present invention may itself be a composite of two or moreindividual layers (e.g., a combination of a perforated film and a mesh),in which case the above thickness values refer to the entire firstlayer. The unit area weight of the first layer, including anyantimicrobial metal which may be combined therewith (in particular,silver), preferably is in the range of from about 10 g/m² to about 40g/m², e.g., about 25 g/m² (as determined by DIN EN 29073-1).

[0057] It should also be noted that the first layer of the composite ofthe present invention may have a variety of substances on the surfacethereof which is to contact the wound, provided these substances do notinterfere to any significant extent with the liquid-permeability of thelayer and the antimicrobial effect exerted by the metal. Non-limitingexamples of such substances are compounds and compositions which promotewound healing and/or have a skin care effect.

[0058] Non-limiting examples of preferred materials for use in or as thefirst layer of the composite of the present invention are polyethylenenets available under the trade name Delnet® (Applied ExtrusionTechnologies, Wilmington, Del.). These nets are produced by extrusion,embossing and stretching of films. A huge variety of these nets iscommercially available and may be produced by altering the polymerblend, the melt temperature, the embossing pattern, and the stretchratio.

[0059] The second layer of the composite of the present invention willusually be liquid-absorbing, or at least liquid-permeable. Where thesecond-layer is (merely) liquid-permeable, the second layer may be thesame as, or similar to the first layer, and in this case the abovecomments with respect to the first layer may be referred to with respectto properties, structure, etc. of the second layer.

[0060] The second layer of the composite of the present inventionpreferably is a liquid-absorbing layer. The term “liquid-absorbing” asused in the present specification and in the appended claims denotes amaterial which is capable of not only taking up a certain amount ofliquid (fluid), but also of retaining the liquid within its structureunder atmospheric pressure. Usually, a liquid-absorbing material will becapable of retaining an amount of liquid which equals at least about 5%,preferably at least about 10% of its own weight.

[0061] The liquid-absorbing capacity of the preferred liquid-absorbingsecond layer of the composite of the present invention (determinedaccording to DIN 53923) will usually be at least about 300 g/m², e.g.,at least about 400 g/m², or at least about 500 g/m², but will usuallynot be higher than about 2000 g/m², e.g., not higher than about 1500g/m², not higher than about 1000 g/m², or not higher than about 800g/m². However, higher liquid-absorbing capacities than those given abovemay be more appropriate in certain cases, for example, for compressesfor use with larger wounds.

[0062] Where the second layer is liquid-absorbing, the second layer maybe composed of any material that is liquid-absorbing and is compatiblewith the intended use of the composite. Preferably, the liquid-absorbingmaterial will be substantially bioinert. For example, the second layermay comprise a textile sheet and/or a foam, e.g., a polyurethane foam.The textile sheet may comprise, by way of non-limiting example, anonwoven, a fleece, a woven fabric, a knit and/or a felt. Preferredexamples of the liquid-absorbing material include nonwovens, e.g.,nonwovens which are bonded by various technologies such as, e.g.,thermal bonding, stitch-bonding (Malivlies, Maliwatt), carding,spun-lacing, melt blowing, etc.

[0063] By way of non-limiting example, the second layer may comprise oneor more natural, semisynthetic and/or synthetic materials such as, e.g.,viscose, cellulose and derivatives thereof, polyolefins (e.g.,polyethylene and/or polypropylene), polyesters, polyetheresters,polyamides, polyurethanes, hydrocolloids, hydrogels, and in general,materials which are conventionally used for making woundcoverings/dressings.

[0064] The second layer of the composite of the present inventionpreferably has a thickness of at least about 0.3 mm, e.g., at leastabout 0.4 mm, or at least about 0.5 mm. The thickness will usually benot higher than about 2.4 mm, e.g., not higher than about 2.0 mm, or nothigher than about 1.4 mm. Like in the case of the first layer, thesecond layer of the composite of the present invention may itself be acomposite of two or more individual layers (by way of non-limitingexample, a combination of two layers or sheets of differentliquid-absorbing materials such as, e.g, a foam and a textile sheet), inwhich case the above values (and those given below) refer to the entiresecond layer.

[0065] The desirable area weight of the second layer of the composite ofthe present invention depends on the intended use and the type oflamination. For standard bandage products for treating conventionalwounds the area weight of the second, liquid-absorbing layer (e.g., thenonwoven), as determined according to DIN EN 29073, will usually be notlower than about about 80 g/m², e.g., not lower than about 100 g/m², andbe not higher than about 200 g/m², e.g., not higher than about 150 g/m²,or not higher than about 130 g/m². An area weight of about 125 g/m² isparticularly preferred. In certain cases higher area weights than thoseindicated above may be more appropriate, for example, for compresses foruse with larger wounds.

[0066] Additionally, the second (liquid-absorbing) layer may compriseone or more superabsorbers such as, for example, water-insoluble,cross-linked polymers that can swell and form hydrogels to absorb andstore large amounts of liquid (e.g., water), even under pressure. Anon-limiting example of a suitable superabsorber is a polymer whichcomprises recurring units derived from acrylic acid and derivativesthereof. When present at all, the superabsorber(s) will usually bepresent in an amount of from about 0.01% to about 40% by weight, basedon the weight of the second layer.

[0067] The composite of the present invention comprises one or moreantimicrobial metals such as, e.g., Ag, Au, Pd, Pt, Cu, Ir, Zn, Sn, Sb,Bi, and alloys comprising one or more of these metals. A particularlypreferred metal is silver. The term “antimicrobial” as used in thepresent specification and the appended claims is to be understood in itsbroadest sense, and is inclusive of terms like “disinfectant”,“antibacterial”, “antifungal” etc. In particular, “antimicrobial”denotes activity against pathogenic microorganisms of any kind.

[0068] The antimicrobial metal in elemental form may be present betweenthe first and second layers of the composite of the present invention inany form which ensures that metal (ions) will be present on the externalsurface of the first layer (opposite the surface that faces the secondlayer) when this surface is contacted with (aqueous) liquid (water,liquid electrolyte, wound exudate etc.) for a sufficient period of time.Accordingly, the expression “present between the first and secondlayers” as used in the present specification and the appended claimsdoes not exclude, but rather includes, composites in which theantimicrobial metal is present within the first layer and/or within thesecond layer instead of, or in addition to, its presence between thelayers. By way of non-limiting example, the first layer of the compositeof the present invention may be composed of a combination of twoindividual liquid-permeable layers (e.g., a mesh and a perforated filmor two perforated films), and the antimicrobial metal may be sandwichedbetween (e.g., be present at the interface of) these two individuallayers. Thus, the present invention encompasses any composite whereinthe antimicrobial metal in elemental form is present within thecomposite, but substantially no antimicrobial metal in elemental form ispresent on exterior surfaces of the composite. “Substantially noantimicrobial metal in elemental form is present on exterior surfaces ofthe composite” means that no more than trace amounts of antimicrobialmetal, in particular, amounts which by themselves will not give rise toa noticeable antimicrobial effect, are present on exterior surfaces ofthe composite.

[0069] In a preferred embodiment of the composite of the presentinvention, the antimicrobial metal is present as a coating on at leastone of the surfaces of the first and second layers, preferably (atleast) on one of the surfaces of the first layer, although acorresponding coating or the like may also be present on one or bothsides of the second layer.

[0070] The antimicrobial metal may be present as such (i.e., without anyother materials), but it may also be present in any other suitable form,for example, as a layer which comprises the antimicrobial metal andother materials such as, e.g., in the form of a porous polymer matrixwhich contains embedded antimicrobial metal.

[0071] The antimicrobial metal (e.g., silver) will usually be present inan amount of at least about 1 mg/m², e.g., at least about 10 mg/m², atleast about 50 mg/m², at least about 60 mg/m², or at least about 70mg/m². Usually the amount of silver will not be higher than about 1g/m², e.g., not higher about 600 mg/m², not higher than about 450 mg/m²,not higher than about 200 mg/m², or not higher than about 80 mg/m² ofthe composite.

[0072] One or more other layers may be arranged between theantimicrobial metal and the first layer and/or the second layer. Forexample, an intermediate layer may be arranged on the surface of thefirst layer (and/or the second layer) onto which the antimicrobial metalis to be applied. The intermediate layer may serve various purposes,e.g., to provide a higher optical density in order to improve theaesthetic appearance (in particular, where the amount of antimicrobialmetal is relatively low) and/or to produce a more uniform coating and/orto promote adhesion of the antimicrobial metal, etc. The intermediatelayer preferably comprises aluminum (e.g., in the form of a thinaluminum metal film produced by deposition from the gas phase), but anyother material(s) can be used as well as long as they are suitable forthe desired purpose(s) and, in particular, do not interfere with therelease of the antimicrobial metal and the antimicrobial activitythereof.

[0073] In a preferred embodiment of the composite of the presentinvention, the first layer of the composite is laminated to the secondlayer (preferably a liquid-absorbing layer such as, e.g., a nonwoven) byusing meltable fibers under heat and pressure. Welding (e.g., ultrasonicwelding) is an example of the various other techniques which may beemployed for this purpose. In the case of spot-welding the bond betweenthe first layer, e.g., a mesh, and the second layer, e.g., aliquid-absorbing nonwoven, tends to be relatively weak, wherefore a typeof bonding with a larger contact area between these layers is preferred.Yet another non-limiting example of the techniques for bonding the firstand second layers together is the use of adhesives. In this case, theutilized adhesive should not significantly interfere with the release ofthe antimicrobial metal (e.g., silver) or cause inconvenience to theuser.

[0074] Preferably, the first layer of the composite of the presentinvention is bonded to the second layer by continuous bonding, e.g.,substantially completely (as opposed to bonding in certain places only,like in the case of, e.g., spot-welding). Where the first layer islaminated to the second layer by using meltable fibers, a sufficientamount of meltable fibers should be used to ensure sufficient resistanceagainst delamination.

[0075] The composite of the present invention (without any additionallayers which may optionally be present, such as, e.g., a backing layeretc.) will preferably have an area weight (as determined according toDIN EN 29073-1) of at least about 50 g/m², e.g., at least about 80 g/m²,and not more than about 300 g/m², e.g., not more than about 230 g/m², ornot more than about 160 g/m². Also, the composite preferably has athickness (as determined according to DIN EN 29073-2) which is not lowerthan about 0.4 mm, e.g., not lower than about 0.5 mm, and not higherthan about 2.5 mm, e.g., not higher than about 1.4 mm. Furthermore, thecomposite will usually show a peeling or delamination strength (asdetermined according to DIN 53357) of at least about 0.05 N/cm, e.g., atleast about 0.15 N/cm, and not higher than about 1.5 N/cm, e.g., nothigher than about 0.8 N/cm. The minimum single value of the peelingstrength (as determined according to DIN 53357) will usually not belower than 0.05 N/cm. Additionally, the composite will usually show amaximum tensile strength (as determined according to DIN EN 29073-3) offrom about 10 N/cm to about 40 N/cm. Furthermore, the 24-hour release ofantimicrobial metal (e.g., silver) provided by the composite of thepresent invention (as determined according to the method describedhereinbelow) preferably is at least about 0.05 mg/m², particularly, atleast about 0.1 mg/m², but usually it will not be higher than about 3mg/m², e.g., not higher than about 2 mg/m² of composite.

[0076] A wound covering article according to the present invention may,by way of non-limiting example, comprise the above composite and a coveror backing layer arranged on the second layer of the composite (e.g.,directly bonded to the second layer or to any intermediate layer suchas, e.g., a liquid-permeable layer which may optionally be present in acomposite wherein the second layer is made of a liquid-absorbingmaterial). The cover layer may comprise any material that is suitablefor this purpose. Non-limiting examples of corresponding materialsinclude a nonwoven (e.g., composed of polyester), a polyolefin (e.g.polyethylene) film and a combination thereof. The cover layer may carryan adhesive on the surface which is to come into contact with the second(or intermediate) layer and, optionally, also with the skin.Non-limiting examples of suitable adhesives are disclosed in, e.g., DE27 43 979 C3. For example, commercially available pressure-sensitive orUV-curable adhesives based on acrylate or rubber may be used for thispurpose. Preferable is the use of thermoplastic hot-melt adhesives basedon natural and synthetic rubbers and other synthetic polymers such as,e.g., acrylates, methacrylates, polyurethanes, polyolefins, polyvinylderivatives, polyesters and silicones. These adhesives may optionallycontain additives such as, e.g., tackifying resins, softeners,stabilizers and other auxiliary agents. Subsequent cross-linking of theadhesive by UV or electron beam radiation may be advantageous.

[0077] Hot-melt adhesives based on block copolymers, in particular, aredistinguished by their numerous varieties. By specifically lowering theglass transition temperature of the pressure-sensitive adhesive throughselection of the appropriate tackifier, softener, the polymer moleculesize and molecular weight distribution of the individual components, anappropriate adhesion to the skin is ensured also at critical locationsof the human locomotive system.

[0078] It has surprisingly been found that, for example, a woundcovering article which does not have the antimicrobial metal (e.g.,silver) on the surface of a liquid-permeable layer which is to come intocontact with the wound (i.e., not on an external surface thereof), buthas the metal on the opposite surface of the layer, is capable ofreleasing a sufficient amount of the metal to give rise to anantimicrobial (disinfectant) effect when the article is in contact witha wound.

[0079] It is surprising that a wound covering article (e.g., a wounddressing) according to the present invention shows an antimicrobialactivity, as demonstrated by release tests of dissolved silver, as wellas by efficacy studies. These studies demonstrate a marked antibacterialactivity against Escherichia coli and Pseudomonas aeruginosa and asomewhat lower activity against Staphylococcus aureus and Enterococcushirae, in this order.

[0080] A composite according to the present invention is useful, inparticular, as a wound dressing or wound covering such as a compress.Its use in skin care, e.g., as a cosmetic towelette or in baby care isadvantageous as well, particularly, because the antimicrobial metal inelemental form does not directly contact the skin.

[0081] A composite of the present invention in the form of, e.g., awound dressing or other wound covering material which comprises anantimicrobial metal such as silver shows many advantages, including thefollowing:

[0082] upon contact of the silver layer with a wound fluid, silver(ions) is (are) released and exert(s) an antimicrobial effect,

[0083] there is no direct abrasion or release of silver particles intothe wound or onto the skin, which minimizes the risk of complications inwound healing or skin care,

[0084] where a mesh, perforated film or the like is provided as a coverlayer over a textile material (as liquid-absorbing material) fibers fromthe textile material are prevented from being released into the woundand/or adhering to the wound.

[0085] Surprisingly, the structure according to the present inventioncan be realized without, or at least without substantial loss, ofantimicrobial activity. In the case of silver, this activity is observedalready with a very slight coating of silver, and a coating ofpreferably at least about 10 mg silver/m² is particularly preferred toensure satisfactory antimicrobial activity. More silver can also beapplied, e.g., for reasons of the manufacturing process. It has beenshown, for example, that the application of as much as about 600 mg/m²of silver does not harm the user.

[0086] A comparison with known silver-containing wound dressings hasshown that a dressing according to the present invention releases anadvantageously high amount of silver at the beginning of theapplication. Moreover, the release rate is also sufficiently high overan extended period after application; excessive doping with silver is,therefore, not required, and the wound dressing does not have to bereplaced already after a short period of time. This is of greatadvantage to users since they can use the dressing for longer periodswithout loss of antimicrobial (disinfecting) activity.

[0087] Another advantage of a dressing according to the presentinvention is related to abrasion. Rubbing one's finger on the side ofthe dressing which faces the skin reveals no abraded material, let aloneblack discoloration, in contrast to known wound dressings. This isparticularly advantageous, in particular, for aesthetic reasons, fordressings that are used without a physician's supervision.

[0088] In addition to its use as a dressing or wound covering in theform of, e.g., a compress, the composite according to the presentinvention can also be used in other areas, e.g., for skin careapplications. For example, moistened skin may be covered or wiped withthe composite, for example in the form of a cloth. The moisture willpenetrate the cover layer into the moisture-absorbing layer and therebycontact the metal (silver) layer. The antimicrobial metal will bereleased, thereby providing the antimicrobial effect associated with themetal. One of the advantages of the composite of the present inventionis that the skin will not get discolored in these cosmetic uses. This isa substantial improvement over conventionally used products such as,e.g., baby care wipes and dressings.

[0089] Other exemplary embodiments and advantages of the presentinvention may be ascertained by reviewing the present disclosure and theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0090] The present invention is further described in the detaileddescription which follows, in reference to the noted plurality ofdrawings by way of non-limiting examples of exemplary embodiments of thepresent invention, in which like reference numerals represent similarparts throughout the several views of the drawings, and wherein:

[0091]FIG. 1 shows the results of discoloration tests carried out withvarious wound dressings;

[0092]FIG. 2 shows top and cross-sectional schematic views of thegeneral structure of an embodiment of the present invention;

[0093]FIG. 3 shows a top schematic view of an embodiment of the presentinvention in the form of a bandage product; and

[0094]FIG. 4 shows a cross-sectional schematic view of an embodiment ofthe present invention in the form of a bandage product.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0095] The particulars shown herein are by way of example and forpurposes of illustrative discussion of the embodiments of the presentinvention only and are presented in the cause of providing what isbelieved to be the most useful and readily understood description of theprinciples and conceptual aspects of the present invention. In thisregard, no attempt is made to show structural details of the presentinvention in more detail than is necessary for the fundamentalunderstanding of the present invention, the description taken with thedrawings making apparent to those skilled in the art how the severalforms of the present invention may be embodied in practice.

[0096] Abrasion resistance tests were used to examine abrasionresistance. These tests were analogous to the rubbing fastness test fordyes and prints according to DIN 54021. The subsequent evaluation wascarried out according to ISO 105-A03: 1993 with a gray scale of from 1to 5. 1 represents a strong, black discoloration, and 5 represents nodiscoloration at all. The results are shown in FIG. 1, wherein thetested products are identified as follows:

[0097] A: Acticoat®; grayness: 3

[0098] B: silver-coated dressing, silver facing the skin; grayness: 2

[0099] C: dressing according to the invention, manufactured as describedbelow; grayness: 5

[0100] The dressing according to the present invention (FIG. 1, C) has agrayness of 5, i.e., shows no discoloration. The comparative products,on the other hand, show discolorations with a grayness of 2 to 3. Thisadvantageous reduction of abrasion in the case of the product of theinvention is advantageous, especially, for aesthetic reasons.

[0101]FIG. 2 shows top and cross-sectional schematic views of thegeneral structure of an embodiment of the composite according to thepresent invention. A liquid-permeable layer (2) is laminated onto aliquid-absorbing layer (1). On the side which faces layer (1), layer (2)is coated with silver (3). In a preferred embodiment, a layer ofaluminum (4) is arranged between layer (1) and the silver coating (3).The aluminum layer makes it easier to coat the silver more uniformly andimproves the appearance.

[0102] The composite according to the present invention is particularlysuitable for use in, or as a wound dressing for self-adhesive bandageproducts, and also as an isolated wound covering that may beadditionally fastened to the wound.

[0103]FIGS. 3 and 4 show top and cross-sectional schematic views ofanother embodiment of a material according to the present invention inthe form of an adhesive strip. The dressing (A) which comprises thefollowing layers:

[0104] liquid-absorbing layer (1)

[0105] liquid-permeable layer (2)

[0106] aluminum layer (4)

[0107] silver layer (3)

[0108] is provided on a backing layer (5) which is coated with anadhesive layer (6). The strip thus has a structure which is similar tothat of classic bandages. Prior to use, the adhesive layer and the woundcovering may be covered with a sealing paper (7).

[0109] Where additional adhesion is desired, the dressing according tothe invention can be adhered to the skin by adding adhesive around theedge as shown in FIG. 3. In this case, the dressing according to thepresent invention will have a structure similar to that of known woundbandages. Peripheral adhesion is possible as in the case of bandages, asis adhesion on both sides as in the case of rolled stock.

[0110] The dressing material according to the present invention—with orwithout additional edge adhesive—may be placed on a wound in the usualway, with substantially no elemental silver coming into contact with thewound.

[0111] Once the silver-containing dressing is removed, the antibacterialeffect ceases. Usually, the skin or wound will not have to be washed asno antiseptics and antibiotics will have to be removed.

EXAMPLE

[0112] A commercially available polyethylene net (Delnet®, availablefrom Applied Extrusion Technologies, and also available from Smith &Nephew Extruded Films Ltd. U.K.), having triangle-shaped holes (lengthof longest bisector: 400-700 μm) is coated, by vapor deposition, firstwith aluminum and then with silver (alternatively, a commerciallyavailable PE net that already is coated with aluminum may be used). Thearea weight of the resultant Al and Ag coated net is about 20 g/m². Thecontent of Al is about 60-80 mg/m² and the content of Ag is about 60-460mg/m². The coated net is laminated to a needle-punched nonwoven(Malivlies) with the coated side facing the nonwoven. The nonwoven iscomposed of about 75 weight-% of rayon (viscose) and about 25 weight-%of polyethylene/polypropylene fibers and has an area weight of about 120g/m². Lamination is carried out under heat and pressure (by slightlymelting the PE/PP fibers and pressing the two layers together).

[0113] A material which was made as described above showed the followingproperties:

[0114] Area weight (DIN EN 29073-1): 125 g/m²

[0115] Thickness (DIN EN 29073-2): 0.75 mm

[0116] Maximum tensile strength (DIN EN 29073-3): 15.8 N/cm

[0117] Delamination/peeling strength (DIN 53357): 0.95 N/cm

[0118] Minimum single value of delamination/peeling strength (DIN53357): 0.40 N/cm

[0119] Liquid absorption (DIN 53923): 620 g/m²

[0120] Release of silver (see the method described below): 0.46 mg/lafter 24 h

[0121] Efficacy: The antimicrobial activity against Staphylococcusaureus, Enterococcus hirae, Escherichia coli, Pseudomonas aeruginosa andCandida albicans was tested. It was found that in all cases the materialshowed bactericidal, bacteriostatic and/or fungicidal activity.

[0122] Method of Determining Release of Silver:

[0123] The release of silver was determined by an extraction of thesilver from a sample of the material (square with a side of 30 +/−1 cm)into a phosphate-buffered saline solution (15 ml of PBS solution) at 31°C. for 24 h. The PBS solution is described by Dulbecco (John Paul,“Zell- und Gewebekulturen”, Walter de Gruyter Publishers, 1980, p. 92).The content of Ca and Mg ions was adjusted to wound fluid levels (0.19g/L of CaCl₂×2 H₂O; 0.27 g/L of MgSO₄×7 H₂O; Geigy Scientific Tables,Vol. 3, Ciba-Geigy Ltd., 8th Ed. 1984, p 82). Following the extraction,the sample was carefully removed from the solution. The aqueous phasewas acidified and the silver concentration was determined by atomicabsorption spectroscopy using an air/C₂H₂ flame at a wavelength of 328.1nm.

[0124] It is noted that the foregoing examples have been provided merelyfor the purpose of explanation and are in no way to be construed aslimiting of the present invention. While the present invention has beendescribed with reference to an exemplary embodiment, it is understoodthat the words which have been used herein are words of description andillustration, rather than words of limitation. Changes may be made,within the purview of the appended claims, as presently stated and asamended, without departing from the scope and spirit of the presentinvention in its aspects. Although the present invention has beendescribed herein with reference to particular means, materials andembodiments, the present invention is not intended to be limited to theparticulars disclosed herein; rather, the present invention extends toall functionally equivalent structures, methods and uses, such as arewithin the scope of the appended claims.

What is claimed is:
 1. An antimicrobial composite comprising a first,liquid-permeable layer and a second layer arranged on the first layer,wherein an antimicrobial metal in elemental form is present between thefirst and second layers and substantially no antimicrobial metal inelemental form is present on exterior surfaces of the composite.
 2. Thecomposite of claim 1, wherein the first layer comprises a foramenousmaterial.
 3. The composite of claim 1, wherein the first layer comprisesat least one of a hole and a mesh structure.
 4. The composite of claim2, wherein the first layer comprises at least one of a perforated filmand a mesh.
 5. The composite of claim 1, wherein the first layercomprises an organic polymer.
 6. The composite of claim 5, wherein theorganic polymer comprises a polyolefin.
 7. The composite of claim 6,wherein the polyolefin comprises at least one of polyethylene andpolypropylene.
 8. The composite of claim 1, wherein the first layercomprises a polyethylene mesh.
 9. The composite of claim 1, wherein thefirst layer comprises openings having a size of from about 250 μm toabout 1400 μm.
 10. The composite of claim 8, wherein the polyethylenemesh comprises openings having a size of from about 400 μm to about 700μm.
 11. The composite of claim 10, wherein the openings have asubstantially triangular shape.
 12. The composite of claim 9, whereinthe openings provide an open area of from about 15% to about 60% of thesurface area of the first layer.
 13. The composite of claim 2, whereinthe first layer has a thickness of from about 0.02 mm to about 0.8 mm.14. The composite of claim 3, wherein the first layer has a thickness offrom about 0.05 mm to about 0.5 mm.
 15. The composite of claim 1,wherein the second layer is one of a liquid-permeable layer and aliquid-absorbing layer.
 16. The composite of claim 4, wherein the secondlayer comprises at least one of a perforated film and a mesh.
 17. Thecomposite of claim 2, wherein the second layer comprises an organicpolymer.
 18. The composite of claim 17, wherein the organic polymercomprises a polyolefin.
 19. The composite of claim 4, wherein the secondlayer comprises a polyethylene mesh.
 20. The composite of claim 1,wherein the second layer has a thickness of from about 0.02 mm to about2.5 mm.
 21. The composite of claim 15, wherein the second layer is aliquid-absorbing layer.
 22. The composite of claim 21, wherein theliquid-absorbing layer has a liquid-absorbing capacity of from about 300g/m² to about 2000 g/m².
 23. The composite of claim 22, wherein theliquid-absorbing capacity is from about 400 g/m² to about 1000 g/m². 24.The composite of claim 21, wherein the second layer comprises a textilesheet.
 25. The composite of claim 24, wherein the textile sheetcomprises at least one of a nonwoven, a fleece, a fabric, a knit and afelt.
 26. The composite of claim 21, wherein the second layer comprisesat least one of fibers and yarns.
 27. The composite of claim 25, whereinthe second layer comprises at least one of viscose, polyolefin andpolyester.
 28. The composite of claim 27, wherein the polyolefincomprises at least one of polyethylene and polypropylene.
 29. Thecomposite of claim 21, wherein the second layer has a thickness of fromabout 0.3 mm to about 2.4 mm.
 30. The composite of claim 24, wherein thesecond layer has a thickness of from about 0.5 mm to about 1.4 mm. 31.The composite of claim 21, wherein the second layer has an area weightof from about 80 g/m² to about 200 g/m².
 32. The composite of claim 31,wherein the second layer comprises a superabsorber.
 33. The composite ofclaim 32, wherein the superabsorber comprises a polymer having recurringunits derived from acrylic acid and derivatives thereof.
 34. Thecomposite of claim 32, wherein the superabsorber is present in an amountof from about 0.01% to about 40% by weight, based on the second layer.35. The composite of claim 1, wherein the antimicrobial metal comprisesat least one of Ag, Au, Pd, Pt, Cu, Ir, Zn, Sn, Sb, Bi and alloyscomprising one or more of these metals.
 36. The composite of claim 2,wherein the antimicrobial metal comprises Ag and alloys thereof.
 37. Thecomposite of claim 1, wherein the antimicrobial metal is provided as acoating on at least one of the surfaces of the first and second layers.38. The composite of claim 1, wherein the antimicrobial metal is presentas a layer which comprises the antimicrobial metal and is arrangedbetween the first and second layers.
 39. The composite of claim 1,wherein the composite has a sheet-like structure.
 40. The composite ofclaim 39, wherein the antimicrobial metal is present in an amount offrom about 1 mg/m² to about 1 g/m².
 41. The composite of claim 40,wherein the antimicrobial metal comprises at least one of Ag, Cu, Zn andan alloy of one or more of these metals.
 42. The composite of claim 41,wherein the antimicrobial metal comprises silver and is present in anamount of from about 10 mg/m² to about 600 mg/m².
 43. The composite ofclaim 42, wherein the silver is present in an amount of from about 50mg/m² to about 450 mg/m².
 44. The composite of claim 43, wherein thesilver is present in an amount of from about 60 mg/m² to about 80 mg/m².45. The composite of claim 3, wherein the first layer has a silvercoating on a surface thereof which faces the second layer.
 46. Thecomposite of claim 3, wherein the second layer has a silver coating on asurface thereof which faces the first layer.
 47. The composite of claim45, wherein an intermediate layer is arranged between the silver coatingand the first layer.
 48. The composite of claim 47, wherein theintermediate layer comprises aluminum.
 49. The composite of claim 1,wherein the first layer is coated with aluminum on one side thereof. 50.The composite of claim 1, wherein the composite has an area weight offrom about 50 g/m² to about 300 g/m².
 51. The composite of claim 42,wherein the composite has an area weight of from about 80 g/m² to about160 g/m².
 52. The composite of claim 1, wherein the composite has athickness of from about 0.4 mm to about 2.5 mm.
 53. The composite ofclaim 42, wherein the composite has a thickness of from about 0.5 mm toabout 1.4 mm.
 54. The composite of claim 1, wherein the composite showsa peeling strength of from about 0.05 N/cm to about 1.5 N/cm.
 55. Thecomposite of claim 51, wherein the composite shows a peeling strength offrom about 0.15 N/cm to about 0.8 N/cm.
 56. The composite of claim 1,wherein the composite shows a maximum tensile strength of from about 10N/cm to about 40 N/cm.
 57. The composite of claim 40, wherein thecomposite shows a 24-hour release of the antimicrobial metal of fromabout 0.05 mg/m to about 3 mg/m .
 58. The composite of claim 42, whereinthe composite shows a 24-hour release of the silver of from about 0.1mg/m² to about 2 mg/m².
 59. The composite of claim 51, wherein thecomposite has a size of at least about 0.5 cm.
 60. The composite ofclaim 50, wherein the composite has a size of not more than about 1 m².61. An antimicrobial composite comprising a first, liquid-permeablelayer and a second, liquid-absorbing layer on the first layer, whereinthe first layer comprises a coating of elemental silver on a side whichfaces the second layer, the second layer comprises a nonwoven whichcomprises at least one of polyethylene, polypropylene, polyester andviscose, and wherein substantially no silver metal is present onexterior surfaces of the composite.
 62. The composite of claim 61,wherein the first layer comprises a polyethylene mesh.
 63. The compositeof claim 61, wherein the first layer has a thickness of from about 0.05mm to about 0.5 mm.
 64. The composite of claim 63, wherein the secondlayer has a thickness of from about 0.5 mm to about 1.4 mm.
 65. Thecomposite of claim 62, wherein the second layer has a liquid-absorbingcapacity of from about 400 g/m² to about 800 g/m².
 66. The composite ofclaim 64, wherein the second layer has an area weight of from about 80g/m² to about 150 g/m².
 67. The composite of claim 61, wherein thesilver is present in an amount of from about 50 mg/m² to about 450mg/m².
 68. The composite of claim 62, wherein an aluminum coating isarranged between the silver coating and the first layer.
 69. Thecomposite of claim 61, wherein the composite has an area weight of fromabout 80 g/m² to about 160 g/m².
 70. The composite of claim 69, whereinthe composite has a thickness of from about 0.4 mm to about 2.5 mm. 71.The composite of claim 69, wherein the composite shows a 24-hour releaseof silver of from about 0.1 mg/m² to about 2 mg/m².
 72. A wound coveringarticle comprising the composite of claim
 1. 73. A wound coveringarticle comprising the composite of claim
 61. 74. A wound coveringarticle comprising an antimicrobial composite which comprises a first,liquid-permeable layer and a second layer over the first layer, whereinan antimicrobial metal in elemental form is present between the firstand second layers, the article further comprising a backing materialarranged on the second layer.
 75. The article of claim 74, wherein thebacking material carries an adhesive on a surface which faces the secondlayer of the composite.
 76. The article of claim 75, wherein theadhesive comprises one of a UV-curable acrylic adhesive and arubber-based hot melt adhesive.
 77. The article of claim 75, wherein thebacking material comprises at least one of a polyester nonwoven and apolyethylene film.
 78. The article of claim 72, which is one of a wounddressing, a compress, and a bandage.
 79. A bandage which comprises thewound covering article of claim
 77. 80. An antimicrobial skin carearticle which comprises the composite of claim
 61. 81. A diaper whichcomprises the composite of claim
 1. 82. A method of covering a wound,wherein the method comprises placing the wound covering article of claim72 on the wound so that the first layer of the composite contacts thewound.
 83. A method of covering a wound, wherein the method comprisesplacing the wound covering article of claim 73 on the wound so that thefirst layer of the composite contacts the wound.
 84. A method ofcovering a wound, comprising providing a material which comprises aliquid-permeable layer and an antimicrobial metal in elemental formassociated with this layer, and placing the material on the wound sothat a surface of the liquid-permeable layer which is substantially freeof the antimicrobial metal in elemental form contacts the wound.
 85. Themethod of claim 84, wherein the liquid-permeable layer comprises aforamenous material.
 86. The method of claim 85, wherein theliquid-permeable layer comprises at least one of a perforated film and amesh.
 87. The method of claim 85, wherein the liquid-permeable layercomprises a polyolefin mesh.
 88. The method of claim 84, wherein theliquid-permeable layer comprises openings having a size of from about250 μm to about 1400 μm.
 89. The method of claim 88, wherein theliquid-permeable layer has thickness of from about 0.02 mm to about 0.8mm.
 90. The method of claim 84, wherein the antimicrobial metalcomprises at least one of Ag, Au, Pd, Pt, Cu, Zn, and alloys comprisingone or more of these metals.
 91. The method of claim 85, wherein theantimicrobial metal comprises Ag and alloys thereof.
 92. The method ofclaim 91, wherein the material shows a 24-hour release of silver of fromabout 0.05 mg/m² to about 3 mg/m² of material.
 93. The method of claim84, wherein the material further comprises a second layer which isarranged on a side of the liquid-permeable layer which has theantimicrobial metal thereon.
 94. The method of claim 93, wherein thesecond layer is a liquid-absorbing layer.
 95. A process of making anantimicrobial composite, the process comprising bonding together afirst, liquid-permeable material and a second material which is at leastone of liquid-permeable and liquid-absorbing, wherein at least one ofthe first and second materials is coated with an antimicrobial metal inelemental form on a surface thereof which faces the other material, andwherein substantially no antimicrobial metal in elemental form ispresent on an exterior surface of the resultant composite.
 96. Theprocess of claim 95, wherein the process comprises providing aliquid-permeable, sheet-like material, coating one side of the materialwith an antimicrobial metal in elemental form and bonding aliquid-absorbing material to a side of the liquid-permeable materialwhich has the antimicrobial metal thereon.
 97. The process of claim 96,wherein the liquid-permeable material comprises at least one of a holeand a mesh structure.
 98. The process of claim 95, wherein theliquid-permeable material comprises at least one of a perforated filmand a mesh.
 99. The process of claim 96, wherein the antimicrobial metalcomprises at least one of Ag, Au, Pd, Pt, Cu, Zn, and alloys comprisingone or more of these metals.
 100. The process of claim 99, wherein theliquid-permeable material is coated with the metal by a technique whichcomprises vapor deposition.
 101. The process of claim 100, wherein thevapor deposition comprises at least one of vacuum evaporation,sputtering, ion-beam assisted deposition, ion plating and magnetronsputtering.
 102. The process of claim 96, wherein the liquid-permeablematerial has an intermediate coating on a surface thereof which is to becoated with the antimicrobial metal.
 103. The process of claim 102,wherein the intermediate coating comprises aluminum.
 104. The process ofclaim 95, wherein the liquid-absorbing material and the liquid-permeablematerial are bonded to each other by at least one of lamination under atleast one of heat and pressure, gluing, welding, and sewing.